In a direct injection gasoline engine, it is likely that fuel injected into a combustion chamber may adhere to a piston. If adhering fuel is not vaporized by an ignition timing, the adhering fuel is not combusted, which generates a lot of particulate matters (PM). Especially, in a case that piston temperature is relatively low, the fuel is less easily vaporized.
JP-2009-103106A shows that the fuel is injected at the time the piston is positioned at a vicinity of its intake bottom dead center if the piston temperature is low, whereby it is restricted that the fuel adheres to the piston.
However, JP-2009-103106A does not disclose a specific way of detecting piston temperature. A temperature sensor can not be directly provided to the piston. Thus, it is difficult to obtain accurate piston temperature.
Further, since the fuel injection timing is varied from an appropriate timing to a timing around its intake bottom dead center, fuel economy and emission may be deteriorated.